High performance liquid chromatography (HPLC) and ultra performance liquid chromatography (UPLC) systems typical typically include a sample compartment that is adapted for receiving a number of sample vials or wells each containing a sample for analysis. Sample vials are arranged in one or more sample trays that can be loaded into and removed from the sample compartment by a user. Some systems include an auto-sampler that utilizes an automated process to control the position and movement of a sample needle within the sample compartment. For example, the sample needle may be moved to the location of a sample vial. The sample needle is then inserted into the sample vial to extract the sample and to subsequently inject the sample into a high pressure mobile phase.
The temperature of a sample can influence the results of liquid chromatography analysis; therefore it is desirable to maintain the sample compartment within a limited temperature range so that variations in the compartment temperature do not significantly affect measurement accuracy and repeatability. For example, the sample compartment may be cooled to a temperature below the ambient temperature using thermoelectric cooling. One or more fans generate an airflow that is directed across the cooling system and through the sample compartment.
Leakage from the compartment and infiltration of ambient air into the compartment can adversely affect thermal control. The compartment may be cooled relative to the ambient environment. Consequently, water or other forms of condensate can condense on cold surfaces that are exposed to the ambient environment.